von Willebrand Factor Antigen : 1000993

The aliquot must remain frozen. Freeze thaw cycle will adversely affect specimen integrity. CRITICAL FROZEN: Separate specimens must be submitted when multiple tests are ordered.

Test Code
VWG or 1000993

Alias/See Also
Von Willebrand Ag; Von Willebrand Antigen

CPT Codes

Blue top tube, 3.2% sodium citrate.
• Obtain venous blood by clean venipuncture. Avoid slow-flowing draws and/or traumatic venipunctures as either of these may result in an activated or clotted specimen. Do not use needles smaller than 23 gauge. Do not leave the tourniquet on for an extended length of time before drawing the sample.
• A pilot tube (non-additive or light blue tube) before drawing coagulation specimens in light blue vacuum tubes is only necessary when using a butterfly blood collection set as this will cause reduced draw volume in the first tube. Discard the pilot tube.
• Fill light blue tubes as far as vacuum will allow and mix by gentle inversion. Exact ratio of nine parts blood to one part anticoagulant must be maintained. Inadequate filling of the sample tube will alter this ratio and may lead to inaccurate results. Patients who have hematocrit values above 55 percent should have the anticoagulant adjusted to maintain the 9:1 ratio. Use the following formula to determine the amount of anticoagulant to use: [(100 – Hct) / (595 – Hct) ]* total volume = amount of anticoagulant required.
• After collecting the blood, examine the tube to ensure that it is filled to within 90% of the fill line.
• Note: Specimens containing heparin should not be used for coagulation studies. If possible, stop heparin therapy before the draw to avoid contamination. Heparin interferes with most clotting assays. If heparinized line must be used to obtain the sample, flush line with 5mL saline and discard the first 5 mL of blood drawn into a syringe, or 6 “dead space” volumes of the line.

Transport Container
Blood collected in 3.2% sodium citrate (light blue top tube). Proper blood to anticoagulant ratio is required. The tubes must be at a 100 ± 10% fill volume to maintain the correct ratio. Centrifuge light blue-top tube at 1500 g for no less than 15 minutes or speed/time to consistently yield platelet-poor plasma (<10,000/µL). Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer, and place into a plastic transport tube (Min. 0.5 mL). Immediately freeze the aliquot and ship on dry ice.

Transport Temperature

Specimen Stability
After separation from cells: Ambient: Unacceptable; Refrigerated: Unacceptable; Frozen: 30 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Marked hemolysis; marked icterus; moderate to marked lipemia; received thawed; received refrigerated; received room temperature


Setup Schedule
Monday - Friday

Report Available
1-4 days

Reference Range
50-200 %

Clinical Significance
Quantitative determination of von Willebrand Factor Antigen in plasma by the immunoturbidimetric method.

Von Willebrand Factor (VWF) is a multimeric plasma glycoprotein synthesized by endothelial cells and megakaryocytes. Once released in the bloodstream from endothelial cells, some of it may be digested by plasmin and some may be incorporated in the α-granules of platelets by endocytosis. VWF is involved in primary hemostasis and in the coagulation process. It plays an important role in the adhesion of platelets to the vascular subendothelium and in the formation of thrombi via its linkages with the glycoprotein complexes Ib/IX and IIb/IIIa. In the coagulation process, vWF serves as a carrier for Factor VIII (anti-hemophilic factor A) and protects it from degradation.


Von Willebrand Disease (vWD) is the most common inherited bleeding disorder. Clinically, it is often characterized by mucocutaneous hemorrhages.

Three principal types of vWD have been defined:

A. Type 1 corresponds to a quantitative deficiency of vWF. Its transmission is autosomal dominant.
Type 1 is the most frequently encountered (70 – 80% of vWD).

B. Type 2 refers to a qualitative deficiency of vWF. The defect is often located in the multimeric structure.
Its transmission is autosomal dominant or recessive.

C. Type 3 is characterized by a virtual total absence of vWF in both the plasma and cellular compartments.
Its transmission is autosomal recessive.

VWF deficiencies may also be associated with several clinical states such as myeloma, lymphoma, systemic lupus erythematosus, hypothyroidism, etc. These cases may be referred to as acquired von Willebrand diseases.

VWF is a protein involved in inflammation. Its level increases when there are damages of the vascular endothelium as in the postoperative period, during infection, in cancer, and in renal or hepatic disorders.

Performing Laboratory
med fusion

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.